Wireless computer network environments generally comprise a plurality of wireless access points that, when operating in the infrastructure mode, bridge wireless traffic between a wired computer network and the wireless clients that associate with the access points. A wireless Local Area Network (WLAN) is a wireless communication system with radios having relatively high throughput and short coverage ranges. Many wireless LANs are based on iterations of the IEEE 802.11 standard. When a wireless client initializes or moves into an entirely new coverage area, according to the 802.11 standard, it transmits probe requests to locate access points to which it may associate to establish a wireless connection. Often, the wireless client may detect multiple access points. The 802.11 standard, however, generally leaves it to the wireless client to decide with which access point to associate. That is, a wireless client scans the available channels in the region and listens to the Beacon or Probe Response Frames transmitted by access points in that region. The wireless client stores the RSSI (Received Signal Strength Indicator) of the Beacon or Probe Response Frames and other relevant information, such as BSSID, encryption (on/off), etc. After finishing the scanning procedure, the wireless client generally selects the access point with the maximum RSSI, given that the selected access point satisfies other requirements (typically, BSSID, and WEP encryption) as well. The wireless client leaves or disassociates with the access point when the RSSI falls under a predefined threshold, such as when the user walks away from the coverage area of the access point. This association process, however, often results in uneven loads across access points, where many wireless clients are connected to only a few access points in a wireless environment, while other access points may remain idle or lightly loaded. That is, as discussed above, the wireless clients make association decisions based on what is best for the wireless client as opposed to what is best for the overall efficiency and performance of the wireless network environment.
As discussed above, the wireless client, therefore, acts only with regard to its own self-interest and, thus, will generally associate with the access point based on received signal strength without regard to the load on the access point (e.g., number of wireless clients, data throughput, etc.). The access point largely has no influence over the decision process at the wireless client except to deny the association requested by the wireless client. Denying the association, generally spurs the wireless client to repeat the process of discovering access points by transmitting probe requests and scanning the air for Beacon and Probe Response Frames. Many wireless clients, however, simply select the same access point as the logic the implement does not take account of previous association denials. Accordingly, this circumstance renders load balancing and other resource management tasks more problematic. In addition, even with wireless clients that take account of previous association denials, the discovery of access points by wireless client devices and having to repeat the process when associations are denied takes time, adversely affecting the operational efficiency of the network and degrading the wireless client user's experience.
The prior art for resource management in the area of wireless LANs addresses the problem of allocation of network resources by placing proprietary and non-standard intelligence in both the client and the access point in order to allow the client to make association decisions with information received from the radio access point. In order to be effective, it must limit the network to a homogenous client and infrastructure base, which typically is associated with proprietary software.
One example of such an infrastructure is found in I. Papanikos and M. Logothetis, A Study on Dynamic Load Balance for IEEE 802.11b Wireless LAN, cited as www.wcl.ee.upatras.gr/m-logo/papers/IEEE80211-P41.pdf, (7 pp.) and noted as posted as of at least 12 Nov. 2002. This reference describes an algorithm in which the client makes an association decision based on: the number of clients associated with the radio access point, the received signal strength indication (RSSI) value of the Probe Request received from the client by the radio access point, and the mean RSSI value of the signals received by the radio access point from other clients associated with the radio access point. The paper concludes that the algorithm does not perform well in the presence of hidden nodes and/or highly asymmetric traffic. Despite taking account of loading conditions, the association decisions are still allocated to the wireless client, which assesses a plurality of weighted factors to select an access point with which to associate. The association selection, however, may nevertheless not be appropriate based on the current loading conditions of the network. The selected access point in this instance will then deny the association request, causing the wireless client to repeat the scanning process.
In light of the foregoing, a need in the art for methods, apparatuses and systems that facilitate load balancing and other tasks associated with wireless network environments. A need further exists for a mechanism that reduces the number of association attempts in wireless computer networks. A need further exists for a mechanism that facilitates roaming in wireless network environments. Embodiments of the present invention substantially fulfill these needs.